My Rule livewell pump lasted about eight months and the replacement Shurflo Piranha barely lasted five months. I replaced the Piranha with a Shurflo Bait Sentry 800 gph. and so far so good at four months. I would stay away from pumps that mount directly through the hull. You don't want a cheap piece of plastic as the only thing keeping water from flooding your boat.
• My bait sentry threads directly to a seacock in the bilge which allows me to stop the flow of water should the pump break off (the Rule broke in my hand when I was removing it). All holes below the waterline need to have a seacock. http://www.groco.net/images/seacocks...ks_BV_BVH.html
The seacock is screwed or bolted to a block of marine plywood epoxied to the bottom of the hull in the bilge.
•There is a high speed scoop on the bottom the boat that threads directly to the seacock from the outside of the hull. Make sure to use plenty of marine sealant 3M 4200 works well. http://www.groco.net/images/fittings/STH-W-500-05.gif
•Run a hose from the livewell pump to the livewell (don't use the cheap ribbed plastic stuff). It should be attached to a spray head near the top of the well (through the well). Similar to this http://www.iboats.com/mall/image/ven...mall/38764.gif
•Most Livewells have a drain at the bottom and a stand pipe. This drain and hose must be large enough to keep up with the inlet hose. The hose drains overboard through a large thru-hull . http://www.groco.net/images/fittings...-ThruHull.html
Some livewells drain at the top with a thru-hull instead of having a drain at the bottom.
I suggest that you visit a boat dealership and take a look at some livewell setups. Perhaps that will help clarify things.
Post some pictures of your boat and that will help us help you decide how to proceed.